It has been known for a very long time to machine mechanical parts by using a hollow cylindrical tool presenting a distal end with a free edge that is shaped to implement machining when said tool is driven in rotation about its axis, the free edge generally being shaped to carry a set of teeth for attacking the material of the mechanical part that is to be machined.
In the field of portable drills, proposals have already been made to remove swarf or shavings via a central channel of the drilling tool and the associated spindle (see for example patent document U.S. Pat. No. 4,711,609).
Other machine tools are sometimes fitted with a central suction system for shavings (see for example patent documents DE-C-929 930, U.S. Pat. No. 2,919,901, and DE-U-200 09 411).
For technological background, reference can also be made to patent documents U.S. Pat. No. 3,382,743 and EP-A-1 093 897.
The machining device used naturally depends on the type of mechanical parts concerned, in particular on their dimensions and above all the materials from which they are made. In this respect, making three-dimensional mechanical parts, e.g. life-sized models of motor vehicle bodywork parts, has led specialists in this technical field to abandon traditional materials such as wood and to turn instead to plastics materials, and in particular polystyrene.
It is thus common practice to make three-dimensional models of motor vehicle components, and in particular bodywork parts, starting from a blank made of polystyrene. In order to achieve a shape for the three-dimensional part that is very precise, it is necessary to undertake machining in which precision is under complete control.
To this end, it is present practice to use milling robots having a machining cutter that rotates at high speed, e.g. about 20,000 revolutions per minute (rpm), with milling being performed with high precision by the robot being moved under the control of a numerical control installation.
Unfortunately, such milling robots present two major drawbacks, that have not been overcome in satisfactory manner.
The first drawback is that of noise, the high speed of the spinning cutter leading to very high frequency noise and whistling that are particularly burdensome for nearby personnel, even though they generally wear helmets with sound protection, thereby de facto excluding the presence on site of other people, because of the discomfort caused.
The second drawback lies in generating relatively fine dust as a result of the milling passes, and removing such dust leads to practical problems inherent both to the size of the particles, and also to the electrostatic charge of said particles which stick to a greater or lesser extent to the surrounding equipment, and in particular to the hinged arm of the milling robot. The dust is thus difficult to remove, and in particular, it is not possible to conceive making use of the suction techniques that are traditionally to be found in installations for removing wood sawdust, using suction that is necessarily applied laterally because of the presence of the outlet shaft of the drive motor on the axis of the tool.
Finally, in addition to the two major drawbacks mentioned above, it should also be observed that the machining device fitted to the milling robot uses a drive motor that is adapted to the speed conditions required, and consequently constitutes a component that is both expensive and fragile. Finally, such motor drive also implies that the installation consumes a non-negligible amount of electrical power.